assigning puplic IP's

hey guys:

so i'm sort of a networking newb, but i've been thrust into this position as our guy took off on us, leaving me to fill in the blanks. here's my deal:

we have a T1 connection, using a SIEMENS se 5940 router. Before now we had always used the default config, DHCP assigning 192.168 addresses, but we recently got a block of public IP's that i need to be able to assign to a number of hosts on our network. I'm just at a loss on how this happens, i've never had to do something like this before.

from what i've been able to gather on the web, i'm missing a piece of the puzzle it sounds like? when i have setup like this, i need something like a hardware firewall?

basically, what must i do to be able to assign these public addresses?